{"gene":"NGFR","run_date":"2026-06-10T05:19:52","timeline":{"discoveries":[{"year":1999,"finding":"p75NTR physically interacts with TrkA, TrkB, and TrkC receptor tyrosine kinases (but not EGFR), as demonstrated by co-immunoprecipitation in transfected cells. Both extracellular and intracellular domains of TrkB and p75NTR contribute to this interaction. Blocking TrkB autophosphorylation substantially reduced interactions involving the intracellular domains. Co-expression of p75NTR with TrkB increased specificity of TrkB activation by BDNF relative to NT-3 and NT-4/5.","method":"Co-immunoprecipitation, deletion construct analysis, kinase inhibition","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP with multiple deletion constructs, domain mapping, functional specificity assay, replicated across multiple Trk receptors in a single rigorous study","pmids":["9927421"],"is_preprint":false},{"year":1996,"finding":"NGF activates a protein kinase (120 and 104 kDa proteins) directly associated with p75(NGFR), co-immunoprecipitated from dorsal root ganglion and PC12 cells. TrkA activation was necessary to elicit p75(NGFR)-associated kinase activity. A 43 amino acid region in the cytoplasmic domain of p75(NGFR) was responsible for accelerating kinase activation at low NGF concentrations, even when NGF binding to p75(NGFR) was not required.","method":"Co-immunoprecipitation, kinase assay, deletion analysis","journal":"The EMBO journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP kinase assay with deletion analysis, single lab, two orthogonal methods","pmids":["8698038"],"is_preprint":false},{"year":2003,"finding":"p75NTR overexpression in primary cortical neurons, PC12 cells, and glioma cells activates JNK, causes cytosolic cytochrome c accumulation, and activates caspases 9, 6, and 3. p75NTR-dependent JNK activation leads to phosphorylation and oligomerization of the BH3-domain-only family member Bad. Loss-of-function using Bad dominant negatives or RNA interference demonstrated a requirement for Bad in p75NTR-induced apoptosis.","method":"Overexpression, loss-of-function (dominant negative, RNAi), biochemical assays for JNK activation, cytochrome c release, caspase activity","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (overexpression + dominant negative + RNAi + biochemical pathway assays) in multiple cell types in one study","pmids":["14673001"],"is_preprint":false},{"year":2009,"finding":"Crystal structure of proNGF complexed with p75NTR resolved at 3.75 Å reveals a 2:2 symmetric binding mode, contrasting with the asymmetric structure of mature NGF bound to p75NTR. The pro regions of proNGF are mostly disordered and two hairpin loops (loop 2) at the top of the NGF dimer undergo conformational changes compared to mature neurotrophin structures. Surface plasmon resonance and cell-based assays showed calcium ions promote formation of a stable ternary complex of proNGF-sortilin-p75NTR.","method":"X-ray crystallography, surface plasmon resonance, cell-based binding assays","journal":"Journal of molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure plus SPR binding assays plus cell-based assays in a single rigorous structural/biochemical study","pmids":["20036257"],"is_preprint":false},{"year":2010,"finding":"In PC12 cells, NGF induces rapid alpha-secretase- and gamma-secretase-dependent cleavage of p75NTR, releasing the intracellular domain (ICD) into the cytosol. This cleavage is mediated by Trk-dependent activation of MEK-Erk signaling and induction of alpha-secretase activity, and is independent of ligand binding to p75NTR. Neurons and PC12 cells lacking p75NTR show defects in neurotrophin-dependent Akt activation that are rescued by full-length p75NTR or the p75 ICD but not cleavage-resistant p75NTR. NGF-dependent growth arrest of PC12 cells requires p75NTR cleavage and ICD generation.","method":"Pharmacological inhibition of secretases, MEK-Erk pathway inhibition, p75NTR knockout neurons, rescue with full-length vs cleavage-resistant constructs, Akt activation assays","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal approaches (pharmacological, genetic KO, domain rescue constructs, functional assays) in a single study","pmids":["20530577"],"is_preprint":false},{"year":2015,"finding":"p75NTR predominantly assembles as a trimer (with monomers and trimers coexisting at the cell surface), as determined by biochemical techniques in vitro and in mouse brain tissue. Trimers are not required for ligand-independent or ligand-dependent p75NTR activation in a growth cone retraction functional assay; monomers are capable of inducing acute morphological effects in neurons.","method":"Biochemical oligomerization assays (in vitro and mouse brain tissue), functional growth cone retraction assay","journal":"The Journal of neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — biochemical and functional assays in a single study, single lab","pmids":["26311773"],"is_preprint":false},{"year":2015,"finding":"NMR spectroscopy of p75NTR transmembrane and intracellular domains in lipid-protein nanodiscs revealed high flexibility and disorder in the juxtamembrane chopper domain, resulting in motions of the death domain being uncoupled from the transmembrane helix. Neither intracellular domain demonstrated propensity to interact with the membrane or to self-associate under these conditions.","method":"Solution NMR spectroscopy in lipid-protein nanodiscs","journal":"Biophysical journal","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — NMR structural data in a defined reconstituted system, single lab, no functional mutagenesis validation","pmids":["26287629"],"is_preprint":false},{"year":2004,"finding":"SC1 (Schwann cell factor 1), a p75NTR-interacting protein, acts as a transcriptional repressor requiring trichostatin A-sensitive HDAC activity (forming a complex with HDACs 1, 2, and 3). SC1 represses the cyclin E promoter, suggesting a mechanism for growth arrest. The zinc finger and PR domains are required for repressive activity, efficient block of BrdU incorporation, and nuclear localization.","method":"Gal4 tethering transcriptional assay, HDAC co-immunoprecipitation, promoter reporter assay, domain deletion analysis, BrdU incorporation","journal":"The Journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with HDACs, functional reporter assays, domain mapping, single lab","pmids":["15051733"],"is_preprint":false},{"year":2006,"finding":"IGF-1 receptor (IGF1-R) signaling, through IRS2, PIP3/Akt, and regulated by PTEN and p44 (short isoform of p53), controls the age-dependent switch from TrkA to p75NTR expression in human neuroblastoma lines and primary mouse neurons. This TrkA-to-p75NTR switch is accompanied by ceramide activation, BACE1 stabilization, and increased amyloid beta-peptide production.","method":"Signaling pathway manipulation (IGF1-R, PTEN, p44 transgenic mice), biochemical assays for ceramide, BACE1, and Abeta","journal":"The EMBO journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — transgenic animal model with multiple biochemical readouts, single lab","pmids":["16619032"],"is_preprint":false},{"year":2015,"finding":"proBDNF activates p75NTR to suppress persistent firing and excitability of entorhinal cortex layer V pyramidal neurons via a Rac1-dependent and PIP2-dependent signaling cascade. proBDNF decreases cholinergic calcium responses in cortical neurons and affects carbachol-induced depletion of PIP2. Genetic deletion of p75NTR specifically in neurons or during adulthood enhances excitability and persistent firing.","method":"Electrophysiological recordings, p75NTR null mice, conditional/inducible p75NTR deletion, function-blocking antibodies, pharmacological probes","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (electrophysiology, genetic KO, antibody blockade, pharmacology) with consistent results across approaches","pmids":["26134656"],"is_preprint":false},{"year":2003,"finding":"Osmotic swelling-induced cell swelling activates transcription of the p75NTR gene via a pathway requiring phospholipase C, protein kinase C, and nitric-oxide synthase activity, independent of de novo protein synthesis.","method":"Reporter gene assay, pharmacological inhibition of PLC, PKC, NOS, tonicity manipulation","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — pharmacological pathway dissection with reporter assay, single lab, multiple inhibitors tested","pmids":["12821676"],"is_preprint":false},{"year":2018,"finding":"proNGF induces tau phosphorylation via p75NTR through the AKT/GSK3β pathway in vitro. Genetic reduction of p75NTR in P301L transgenic mice rescued memory deficits, alleviated tau hyperphosphorylation, and restored AKT/GSK3β pathway activity.","method":"In vitro proNGF treatment, p75NTR genetic reduction in transgenic mice, biochemical pathway analysis (AKT/GSK3β)","journal":"Molecular psychiatry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro mechanistic assay plus in vivo genetic model with pathway readout, single lab","pmids":["29867188"],"is_preprint":false},{"year":2008,"finding":"Two Nogo-66-derived peptides (Pep4 and NEP1-40) that modulate NgR-mediated neurite outgrowth inhibition also prevent NGF-stimulated p75NTR-dependent death of cultured embryonic motor neurons and protect spinal cord motor neurons after neonatal sciatic nerve axotomy, demonstrating that NgR antagonizes p75NTR-dependent motor neuron death.","method":"Cultured embryonic motor neuron survival assay, neonatal sciatic nerve axotomy in vivo","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro and in vivo convergent results, single lab, peptide-based functional inhibition","pmids":["18182498"],"is_preprint":false},{"year":2021,"finding":"Melanoma-derived small extracellular vesicles (sEVs) enriched in NGFR spread through the lymphatic system and are taken up by lymphatic endothelial cells, inducing ERK kinase and NF-κB activation and ICAM-1 expression to enhance lymphangiogenesis and tumor cell adhesion. Ablation or inhibition of NGFR in sEVs reversed the lymphangiogenic phenotype and decreased lymph node metastasis in pre-clinical models.","method":"sEV isolation and characterization, NGFR ablation/inhibition in sEVs, in vivo murine lymphangiogenesis/metastasis models, signaling pathway analysis (ERK, NF-κB, ICAM-1)","journal":"Nature cancer","confidence":"High","confidence_rationale":"Tier 2 / Strong — mechanistic pathway elucidation with NGFR ablation/inhibition rescue experiments in both in vitro and in vivo models, multiple readouts","pmids":["34957415"],"is_preprint":false},{"year":2017,"finding":"In melanoma, CD271 (NGFR) plays a dual role in phenotype switching: the cleaved intracellular domain controls proliferation, while interaction of CD271 with TrkA modulates cell adhesiveness through dynamic regulation of cholesterol synthesis genes.","method":"CD271 expression manipulation, analysis of intracellular domain cleavage products, TrkA interaction studies, gene expression profiling of cholesterol synthesis genes","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — functional domain analysis and interaction study, single lab, mechanistic follow-up but limited reconstitution data available from abstract","pmids":["29215016"],"is_preprint":false},{"year":2016,"finding":"CD271 knockdown in hypopharyngeal cancer cells completely suppressed tumor-forming capability, induced cell-cycle arrest in G0, suppressed ERK phosphorylation, and strongly upregulated CDKN1C. Double knockdown of CD271 and CDKN1C partially rescued cells from G0 arrest. Inhibition of CD271-RhoA signaling by TAT-Pep5 diminished in vitro migration capability.","method":"siRNA knockdown, in vivo/in vitro tumor formation assays, ERK phosphorylation assay, double knockdown epistasis, RhoA pathway inhibition","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — epistasis (double knockdown rescue) plus pathway inhibition, single lab","pmids":["27469492"],"is_preprint":false},{"year":2023,"finding":"Induced expression of Ngfr in the hippocampus of APP/PS1dE9 mice suppressed reactive astrocyte marker Lipocalin-2 (Lcn2), which itself reduced neurogenesis in astroglia. Anti-neurogenic effects of Lcn2 were mediated by Slc22a17; blockage of Slc22a17 recapitulated the pro-neurogenic effect of Ngfr. Long-term Ngfr expression reduced amyloid plaques and tau phosphorylation.","method":"In vivo Ngfr overexpression, histological analysis, single-cell transcriptomics, spatial proteomics, functional knockdown of Lcn2 and Slc22a17","journal":"NPJ Regenerative medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo genetic manipulation with multiple orthogonal readouts (scRNA-seq, spatial proteomics, functional knockdown), single lab","pmids":["37429840"],"is_preprint":false},{"year":2022,"finding":"SorCS3 co-localizes with and binds to p75NTR in GBM cells (confirmed by immunofluorescence and Co-IP), promoting endosomal trafficking of p75NTR to the lysosome for degradation, thereby reducing p75NTR protein levels and suppressing NGF/p75NTR-driven cell invasion and proliferation.","method":"Co-immunoprecipitation, immunofluorescence co-localization, endosomal trafficking assays, proliferation/invasion assays","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — Co-IP plus co-localization plus functional assays, single lab","pmids":["35393432"],"is_preprint":false},{"year":2017,"finding":"p75NTR is expressed on plasmacytoid dendritic cells (pDCs) and its activation modulates immune function through TLR9 signaling, involving differential phosphorylation of interferon regulatory factor 3 and 7. p75NTR activation of pDCs influenced allergen-specific T cell proliferation and cytokine secretion in an NGF concentration-dependent manner.","method":"p75NTR expression characterization on pDCs, TLR9 activation assays, IRF3/7 phosphorylation, T cell proliferation co-culture assays, ovalbumin-induced asthma mouse model","journal":"Frontiers in immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mechanistic signaling assays combined with in vivo model, single lab","pmids":["28861085"],"is_preprint":false},{"year":2020,"finding":"NGFR expression in melanoma drives resistance to T cell attack and BRAF+MEK inhibitors. NGFRhi cells induce the neurotrophic factor BDNF, which contributes to T cell resistance. Pharmacologic NGFR inhibition restores tumor sensitivity to T cell attack in vitro and in melanoma xenografts.","method":"Chronic T cell exposure selection, BRAF+MEK inhibitor treatment, BDNF functional assays, pharmacological NGFR inhibition, melanoma xenograft models","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional rescue by NGFR inhibition in vitro and in vivo, BDNF mechanism identified, single lab","pmids":["32770055"],"is_preprint":false},{"year":2020,"finding":"p75NTR knockout mice exhibit reduced alveolar bone mass. p75NTR positively regulates osteogenic differentiation of ectomesenchymal stem cells (EMSCs) via the PI3K/Akt/β-catenin pathway. The promotive effect of p75NTR overexpression was attenuated by PI3K inhibitor LY294002, and the inhibitory effect of p75NTR knockdown on Runx2 and Col1 expression was reversed by PI3K agonist 740Y-P.","method":"p75NTR knockout mice, micro-CT, RNA-sequencing, lentiviral p75NTR overexpression/knockdown, PI3K pathway pharmacological manipulation","journal":"Cell proliferation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic KO plus pharmacological epistasis with pathway agonist/antagonist, single lab","pmids":["32215984"],"is_preprint":false},{"year":2021,"finding":"In denervated skeletal muscle, pro-BDNF and p75NTR are significantly upregulated, and JNK and NF-κB downstream pathways are activated along with muscle atrophy and inflammation. p75NTR inhibition using LM11A-31 significantly reduced JNK activation and inflammatory cytokines in denervated muscle. Skeletal muscle-specific BDNF knockout reduced pro-BDNF levels, JNK activation, and inflammation.","method":"Sciatic nerve denervation mouse model, p75NTR inhibitor (LM11A-31), skeletal muscle-specific BDNF KO, Western blot, tissue staining","journal":"Life sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological inhibition and genetic KO with consistent results, single lab","pmids":["34678261"],"is_preprint":false},{"year":2023,"finding":"In denervated skeletal muscle, glial cells express Ngfr and are located near neuromuscular junctions close to Thy1/CD90-expressing cells, which provide the main cellular source of NGF post-denervation. Functional communication between these cells is mediated by NGF/NGFR, as recombinant NGF or co-culture with Thy1/CD90-expressing cells increased glial cell number ex vivo.","method":"scRNA-seq/snATAC-seq, sciatic nerve transection model, ex vivo co-culture, recombinant NGF treatment","journal":"iScience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — single-cell genomics plus functional ex vivo co-culture assay, single lab","pmids":["37416457"],"is_preprint":false},{"year":2023,"finding":"NGFR expression in melanoma cells leads to down-regulation of NK cell activating ligands and up-regulation of stearoyl-coenzyme A desaturase (SCD), protecting melanoma cells from NK cell-mediated killing. Pharmacological and siRNA-mediated inhibition of SCD reversed NGFR-induced NK cell evasion in vitro and in vivo.","method":"In vitro and in vivo NK cell cytotoxic assays, NGFR overexpression, SCD pharmacological inhibition, SCD siRNA knockdown, mouse metastasis model with adoptively transferred human NK cells","journal":"Science advances","confidence":"High","confidence_rationale":"Tier 2 / Strong — mechanistic pathway (NGFR→SCD→NK evasion) validated by both pharmacological and genetic (siRNA) inhibition in vitro and in vivo, convergent results","pmids":["36638181"],"is_preprint":false},{"year":2016,"finding":"p75NTR in retinal glia and pericytes mediates ligand-dependent (proNGF) induction of inflammatory cytokines, disruption of the neuro-glia-vascular unit, promotion of blood-retina barrier breakdown, edema, and neuronal death in a streptozotocin mouse model of diabetic retinopathy. p75NTR-dependent inflammation leads to ischemia and pathological angiogenesis through Semaphorin 3A. Antagonists of p75NTR or proNGF suppressed each phase of pathology.","method":"Streptozotocin diabetic retinopathy mouse model, oxygen-induced retinopathy model, p75NTR and proNGF antagonists","journal":"The Journal of neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological antagonism in two in vivo disease models with multiple pathway readouts, single lab","pmids":["27559166"],"is_preprint":false},{"year":2011,"finding":"CD271/p75NTR inhibits the differentiation of mesenchymal stem cells into osteogenic, adipogenic, chondrogenic, and myogenic lineages. CD271+ DDPSCs showed inhibited differentiation into osteoblasts and adipocytes compared to CD271- cells. Forced expression of CD271 in C3H10T1/2 cells (10T271) inhibited differentiation into all four lineages.","method":"FACS sorting of CD271+ subpopulations, forced CD271 overexpression in C3H10T1/2 cells, in vitro multilineage differentiation assays","journal":"Stem cells and development","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — gain-of-function overexpression plus sorted subpopulation comparison across multiple lineages, single lab","pmids":["21142793"],"is_preprint":false},{"year":2020,"finding":"In valproic acid (VPA)-treated neuroblastoma cells, p75NTR and sortilin are upregulated via HDAC inhibition leading to decreased EZH2 and upregulation of transcription factor CASZ1, a positive regulator of p75NTR. VPA favored proNGF-induced p75NTR/sortilin interaction and enhanced JNK activation and apoptosis. Depletion of p75NTR or blocking proNGF/sortilin interaction (neurotensin) reduced apoptotic response.","method":"HDAC inhibitor treatment, EZH2/CASZ1 knockdown, p75NTR and sortilin knockdown, proNGF treatment, JNK activation assay, apoptosis assays","journal":"Apoptosis","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — multiple knockdown approaches with consistent apoptosis readout, single lab","pmids":["32712736"],"is_preprint":false},{"year":2016,"finding":"NGFR knockdown in murine OSCC cells suppressed tumor invasion and metastasis. NGF treatment of NGFR+ OSCC cells increased ESM1 (endocan) expression. ESM1 overexpression conferred an enhanced migratory, invasive, and metastatic phenotype. ESM1 shRNA knockdown in NGFR-overexpressing OSCC cells abrogated tumor growth kinetics and invasive/metastatic properties, placing ESM1 downstream of NGFR in regulating OSCC invasion.","method":"NGFR overexpression/knockdown, NGF stimulation, gene expression array, ESM1 overexpression, ESM1 shRNA knockdown, in vitro migration/invasion assays, in vivo metastasis model","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — epistasis (NGFR→ESM1 pathway) established by rescue/knockdown experiments in vitro and in vivo, single lab","pmids":["27683113"],"is_preprint":false},{"year":2014,"finding":"Stable shRNA-mediated knockdown of CD271 in patient-derived melanoma cells abrogated tumor-initiating and colony-forming capacity. Genome-wide expression profiling linked CD271 to SOX10 and a neural crest stem cell (NCSC) signature, and connected CD271 expression to CD133.","method":"shRNA knockdown, in vivo tumor-initiating assay, genome-wide expression profiling, gene-set enrichment analysis","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — stable loss-of-function with defined functional phenotype plus transcriptomic pathway analysis, single lab","pmids":["24799129"],"is_preprint":false},{"year":2014,"finding":"In human epidermis, CD271 overexpression provokes the switch of keratinocyte stem cells (KSCs) to transit-amplifying (TA) cells, while silencing CD271 induced TA cells to revert to a KSC phenotype (assessed by β1-integrin expression and increased clonogenic ability). CD271(+) TA cells expressed more survivin and keratin 15 and displayed higher proliferative capacity.","method":"CD271 overexpression, siRNA silencing, FACS sorting, clonogenic assay, skin equivalent models","journal":"The Journal of investigative dermatology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — gain- and loss-of-function with multiple functional readouts, single lab","pmids":["25330297"],"is_preprint":false}],"current_model":"NGFR/p75NTR is a multifunctional TNFR superfamily member that physically interacts with Trk receptor tyrosine kinases (TrkA/B/C) through both extracellular and intracellular domains to modulate neurotrophin signaling specificity; undergoes Trk-induced alpha/gamma-secretase-dependent cleavage to release an intracellular domain that potentiates Akt signaling and growth arrest; signals apoptosis through JNK-mediated Bad phosphorylation and cytochrome c/caspase cascade activation; predominantly assembles as a trimer at the cell surface with monomers capable of acute morphological signaling; binds proNGF in a 2:2 symmetric complex (structurally distinct from mature NGF binding) and promotes pro-apoptotic signaling through sortilin co-receptor; activates p75NTR-Rac1-PI4K/PIP2 pathway to suppress cortical pyramidal neuron excitability; mediates osteogenic differentiation via PI3K/Akt/β-catenin signaling; in melanoma, drives immune evasion by upregulating stearoyl-CoA desaturase (SCD) to escape NK cell killing and promotes metastasis via sEV-mediated ERK/NF-κB/ICAM-1 activation in lymphatic endothelial cells; and in cancer contexts acts downstream of NGFR through ESM1 to drive invasion and metastasis."},"narrative":{"mechanistic_narrative":"NGFR (p75NTR), a TNF-receptor superfamily neurotrophin receptor, integrates neurotrophin signaling by physically partnering with the Trk receptor tyrosine kinases TrkA, TrkB, and TrkC through both its extracellular and intracellular domains, an interaction dependent on Trk autophosphorylation that sharpens ligand specificity of Trk activation [PMID:9927421]. The receptor binds the unprocessed precursor proNGF in a 2:2 symmetric mode distinct from mature NGF, and calcium promotes assembly of a stable proNGF–sortilin–p75NTR ternary complex that drives pro-apoptotic signaling [PMID:20036257]. p75NTR couples to opposing fates depending on context: it triggers apoptosis via JNK-dependent phosphorylation and oligomerization of Bad, cytochrome c release, and caspase-9/6/3 activation [PMID:14673001], yet upon NGF stimulation it also undergoes Trk/MEK-Erk-driven alpha- and gamma-secretase cleavage that releases an intracellular domain required for neurotrophin-dependent Akt activation and growth arrest [PMID:20530577]. In the nervous system the receptor controls neuronal excitability through a proBDNF-activated Rac1/PIP2 cascade [PMID:26134656] and contributes to pathological tau phosphorylation via AKT/GSK3β [PMID:29867188]. Beyond neurons, NGFR is a major driver in melanoma and other cancers, where it promotes immune evasion by upregulating stearoyl-CoA desaturase to escape NK-cell killing [PMID:36638181], enhances T-cell and BRAF/MEK-inhibitor resistance through BDNF induction [PMID:32770055], and spreads via NGFR-enriched extracellular vesicles that activate ERK/NF-κB/ICAM-1 in lymphatic endothelium to promote metastasis [PMID:34957415]. It also regulates stem-cell differentiation, both inhibiting multilineage mesenchymal differentiation [PMID:21142793] and positively driving osteogenic differentiation through PI3K/Akt/β-catenin [PMID:32215984].","teleology":[{"year":1996,"claim":"Established that NGF signaling engages an enzymatic activity physically associated with p75NTR, indicating the receptor is not merely a passive binding protein but a signaling platform.","evidence":"Co-IP kinase assay and cytoplasmic-domain deletion analysis in dorsal root ganglion and PC12 cells","pmids":["8698038"],"confidence":"Medium","gaps":["The identity of the associated 120/104 kDa kinase was not established","Whether the kinase association is direct or bridged by another protein is unresolved"]},{"year":1999,"claim":"Defined the physical basis for crosstalk between p75NTR and the Trk family, showing p75NTR directly modulates Trk ligand selectivity.","evidence":"Reciprocal Co-IP with deletion constructs and kinase inhibition across TrkA/B/C in transfected cells","pmids":["9927421"],"confidence":"High","gaps":["Stoichiometry and structural interface of the Trk–p75NTR complex not defined","Whether the interaction is constitutive or ligand-induced in vivo unclear"]},{"year":2003,"claim":"Elucidated the apoptotic effector arm of p75NTR, linking it through JNK to the intrinsic mitochondrial cell-death machinery.","evidence":"Overexpression plus dominant-negative and RNAi loss-of-function with biochemical JNK/cytochrome c/caspase readouts in multiple cell types","pmids":["14673001"],"confidence":"High","gaps":["How ligand engagement activates JNK upstream of Bad is not defined","Does not address how the apoptotic versus survival decision is selected"]},{"year":2009,"claim":"Resolved the structural distinction between proNGF and mature NGF recognition, explaining how the precursor selectively drives the pro-apoptotic co-receptor complex.","evidence":"X-ray crystallography of proNGF–p75NTR, SPR, and cell-based ternary complex assays","pmids":["20036257"],"confidence":"High","gaps":["Structure of the full proNGF–sortilin–p75NTR ternary assembly not solved","Role of the disordered pro region in signaling not defined"]},{"year":2010,"claim":"Identified regulated intramembrane proteolysis as the mechanism converting p75NTR into a soluble intracellular signaling effector that potentiates Akt and growth arrest.","evidence":"Secretase and MEK-Erk inhibition, p75NTR-knockout neurons, and rescue with cleavage-resistant vs intact constructs in PC12 cells","pmids":["20530577"],"confidence":"High","gaps":["Direct molecular targets of the released ICD not identified","How the ICD potentiates Akt mechanistically unresolved"]},{"year":2015,"claim":"Clarified the oligomeric state of the receptor, showing trimers predominate but are dispensable for acute morphological signaling carried by monomers.","evidence":"Biochemical oligomerization assays in vitro and in mouse brain plus growth cone retraction functional assay","pmids":["26311773"],"confidence":"Medium","gaps":["Which signaling outputs require trimers versus monomers is not fully mapped","Single lab, no orthogonal structural validation"]},{"year":2015,"claim":"Connected p75NTR to control of cortical neuron excitability through a defined Rac1/PIP2 signaling cascade activated by proBDNF.","evidence":"Electrophysiology with constitutive, conditional, and inducible p75NTR deletion plus antibody blockade and pharmacology","pmids":["26134656"],"confidence":"High","gaps":["Direct molecular link from p75NTR to Rac1 not defined","Whether sortilin participates in this pathway not tested"]},{"year":2020,"claim":"Defined opposing roles of p75NTR in stem-cell fate, demonstrating it drives osteogenic differentiation via PI3K/Akt/β-catenin in vivo.","evidence":"p75NTR-knockout mice, micro-CT, and PI3K agonist/antagonist epistasis in ectomesenchymal stem cells","pmids":["32215984"],"confidence":"Medium","gaps":["Reconciliation with reports of p75NTR inhibiting multilineage differentiation not addressed","How p75NTR activates PI3K upstream is unclear"]},{"year":2021,"claim":"Revealed a non-cell-autonomous metastatic mechanism in which NGFR cargo in extracellular vesicles reprograms lymphatic endothelium.","evidence":"sEV isolation with NGFR ablation/inhibition and in vivo lymphangiogenesis/metastasis models with ERK/NF-κB/ICAM-1 readouts","pmids":["34957415"],"confidence":"High","gaps":["How NGFR in sEVs activates recipient-cell ERK/NF-κB mechanistically not defined","Receptor for NGFR-bearing sEVs on endothelial cells not identified"]},{"year":2023,"claim":"Established NGFR as a driver of NK-cell immune evasion in melanoma through metabolic rewiring via stearoyl-CoA desaturase.","evidence":"NK cytotoxicity assays with NGFR overexpression and SCD pharmacological/siRNA inhibition in vitro and in metastasis models","pmids":["36638181"],"confidence":"High","gaps":["How NGFR transcriptionally controls SCD and NK ligands is not defined","Whether SCD-driven lipid changes act on NK ligands or membrane properties unresolved"]},{"year":null,"claim":"How a single receptor selects between pro-apoptotic, pro-survival, differentiation, and oncogenic immune-evasion outputs across cell types remains the central unresolved question.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model of how co-receptor (sortilin, Trk), oligomeric state, and proteolysis jointly determine output","Direct intracellular effectors of the cleaved ICD remain unidentified"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0,3,9]},{"term_id":"GO:0048018","term_label":"receptor ligand activity","supporting_discovery_ids":[3]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[5]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[4]},{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[17]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,4,9]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[2]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[23,19]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[13,23]}],"complexes":["proNGF–sortilin–p75NTR ternary complex"],"partners":["TRKA","TRKB","TRKC","SORTILIN","SORCS3","SC1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P08138","full_name":"Tumor necrosis factor receptor superfamily member 16","aliases":["Gp80-LNGFR","Low affinity neurotrophin receptor p75NTR","Low-affinity nerve growth factor receptor","NGF receptor","Low-affinity nerve growth factor receptor p75NGFR","Low-affinity nerve growth factor receptor p75NGR","p75 ICD"],"length_aa":427,"mass_kda":45.2,"function":"Low affinity receptor which can bind to NGF, BDNF, NTF3, and NTF4. Forms a heterodimeric receptor with SORCS2 that binds the precursor forms of NGF, BDNF and NTF3 with high affinity, and has much lower affinity for mature NGF and BDNF (PubMed:24908487). Plays an important role in differentiation and survival of specific neuronal populations during development (By similarity). Can mediate cell survival as well as cell death of neural cells. Plays a role in the inactivation of RHOA (PubMed:26646181). Plays a role in the regulation of the translocation of GLUT4 to the cell surface in adipocytes and skeletal muscle cells in response to insulin, probably by regulating RAB31 activity, and thereby contributes to the regulation of insulin-dependent glucose uptake (By similarity). Necessary for the circadian oscillation of the clock genes BMAL1, PER1, PER2 and NR1D1 in the suprachiasmatic nucleus (SCmgetaN) of the brain and in liver and of the genes involved in glucose and lipid metabolism in the liver (PubMed:23785138). 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swelling induces p75 neurotrophin receptor (p75NTR) expression via nitric oxide.","date":"2003","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/12821676","citation_count":19,"is_preprint":false},{"pmid":"35476985","id":"PMC_35476985","title":"A Cd9+Cd271+ stem/progenitor population and the SHP2 pathway contribute to neonatal-to-adult switching that regulates tendon maturation.","date":"2022","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/35476985","citation_count":18,"is_preprint":false},{"pmid":"28426529","id":"PMC_28426529","title":"Diagnostic Utility of Pax8, Pax2, and NGFR Immunohistochemical Expression in Pediatric Renal Tumors.","date":"2018","source":"Applied immunohistochemistry & molecular morphology : AIMM","url":"https://pubmed.ncbi.nlm.nih.gov/28426529","citation_count":18,"is_preprint":false},{"pmid":"35129860","id":"PMC_35129860","title":"proBDNF/p75NTR promotes rheumatoid arthritis and inflammatory response by activating proinflammatory cytokines.","date":"2022","source":"FASEB journal : official publication of the Federation of American Societies for Experimental Biology","url":"https://pubmed.ncbi.nlm.nih.gov/35129860","citation_count":18,"is_preprint":false},{"pmid":"23430356","id":"PMC_23430356","title":"Adipogenic and osteogenic differentiation of Lin(-)CD271(+)Sca-1(+) adipose-derived stem cells.","date":"2013","source":"Molecular and cellular biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/23430356","citation_count":18,"is_preprint":false},{"pmid":"23268325","id":"PMC_23268325","title":"Nerve growth factor receptor (NGFR): a potential marker for specific molecular subtypes of breast cancer.","date":"2012","source":"Journal of clinical pathology","url":"https://pubmed.ncbi.nlm.nih.gov/23268325","citation_count":18,"is_preprint":false},{"pmid":"35925599","id":"PMC_35925599","title":"Neurotrophin Pathway Receptors NGFR and TrkA Control Perineural Invasion, Metastasis, and Pain in Oral Cancer.","date":"2022","source":"Advanced biology","url":"https://pubmed.ncbi.nlm.nih.gov/35925599","citation_count":17,"is_preprint":false},{"pmid":"35457078","id":"PMC_35457078","title":"Expression of NGF/proNGF and Their Receptors TrkA, p75NTR and Sortilin in Melanoma.","date":"2022","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/35457078","citation_count":17,"is_preprint":false},{"pmid":"32712736","id":"PMC_32712736","title":"Valproic acid upregulates the expression of the p75NTR/sortilin receptor complex to induce neuronal apoptosis.","date":"2020","source":"Apoptosis : an international journal on programmed cell death","url":"https://pubmed.ncbi.nlm.nih.gov/32712736","citation_count":17,"is_preprint":false},{"pmid":"25739328","id":"PMC_25739328","title":"Hypoxia-Inducible Factor-1α and CD271 inversely correlate with melanoma invasiveness.","date":"2015","source":"Experimental dermatology","url":"https://pubmed.ncbi.nlm.nih.gov/25739328","citation_count":17,"is_preprint":false},{"pmid":"27663144","id":"PMC_27663144","title":"Expression of SOX10, ABCB5 and CD271 in melanocytic lesions and correlation with survival data of patients with melanoma.","date":"2016","source":"Clinical and experimental dermatology","url":"https://pubmed.ncbi.nlm.nih.gov/27663144","citation_count":17,"is_preprint":false},{"pmid":"36638181","id":"PMC_36638181","title":"Escape from NK cell tumor surveillance by NGFR-induced lipid remodeling in melanoma.","date":"2023","source":"Science advances","url":"https://pubmed.ncbi.nlm.nih.gov/36638181","citation_count":16,"is_preprint":false},{"pmid":"22201277","id":"PMC_22201277","title":"Biological and clinical significance of p75NTR expression in laryngeal squamous epithelia and laryngocarcinoma.","date":"2011","source":"Acta oto-laryngologica","url":"https://pubmed.ncbi.nlm.nih.gov/22201277","citation_count":16,"is_preprint":false},{"pmid":"12739005","id":"PMC_12739005","title":"NADE (p75NTR-associated cell death executor) suppresses cellular growth in vivo.","date":"2003","source":"International journal of oncology","url":"https://pubmed.ncbi.nlm.nih.gov/12739005","citation_count":16,"is_preprint":false},{"pmid":"26980374","id":"PMC_26980374","title":"CD271(+) stromal cells expand in arthritic synovium and exhibit a proinflammatory phenotype.","date":"2016","source":"Arthritis research & therapy","url":"https://pubmed.ncbi.nlm.nih.gov/26980374","citation_count":15,"is_preprint":false},{"pmid":"10874514","id":"PMC_10874514","title":"Role of neurotrophin receptor p75NTR in mediating neuronal cell death following injury.","date":"2000","source":"Clinical and experimental pharmacology & physiology","url":"https://pubmed.ncbi.nlm.nih.gov/10874514","citation_count":15,"is_preprint":false},{"pmid":"37047730","id":"PMC_37047730","title":"The Impact of BDNF, NTRK2, NGFR, CREB1, GSK3B, AKT, MAPK1, MTOR, PTEN, ARC, and SYN1 Genetic Polymorphisms in Antidepressant Treatment Response Phenotypes.","date":"2023","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/37047730","citation_count":15,"is_preprint":false},{"pmid":"30154865","id":"PMC_30154865","title":"Induction of Expression of CD271 and CD34 in Mesenchymal Stromal Cells Cultured as Spheroids.","date":"2018","source":"Stem cells international","url":"https://pubmed.ncbi.nlm.nih.gov/30154865","citation_count":14,"is_preprint":false},{"pmid":"26408608","id":"PMC_26408608","title":"A role for NGF and its receptors TrKA and p75NTR in the progression of COPD.","date":"2016","source":"Biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/26408608","citation_count":14,"is_preprint":false},{"pmid":"25392568","id":"PMC_25392568","title":"Expression of p75(NGFR), a Proliferative and Basal Cell Marker, in the Buccal Mucosa Epithelium during Re-epithelialization.","date":"2014","source":"Acta histochemica et cytochemica","url":"https://pubmed.ncbi.nlm.nih.gov/25392568","citation_count":14,"is_preprint":false},{"pmid":"35393432","id":"PMC_35393432","title":"SorCS3 promotes the internalization of p75NTR to inhibit GBM progression.","date":"2022","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/35393432","citation_count":14,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":47022,"output_tokens":7905,"usd":0.129821,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":17468,"output_tokens":3572,"usd":0.08832,"stage2_stop_reason":"end_turn"},"total_usd":0.218141,"stage1_batch_id":"msgbatch_013a8chtv3AWyTqv4z4sEF4C","stage2_batch_id":"msgbatch_01AHsuW63vinsvuTgzmQ3n62","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1999,\n      \"finding\": \"p75NTR physically interacts with TrkA, TrkB, and TrkC receptor tyrosine kinases (but not EGFR), as demonstrated by co-immunoprecipitation in transfected cells. Both extracellular and intracellular domains of TrkB and p75NTR contribute to this interaction. Blocking TrkB autophosphorylation substantially reduced interactions involving the intracellular domains. Co-expression of p75NTR with TrkB increased specificity of TrkB activation by BDNF relative to NT-3 and NT-4/5.\",\n      \"method\": \"Co-immunoprecipitation, deletion construct analysis, kinase inhibition\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP with multiple deletion constructs, domain mapping, functional specificity assay, replicated across multiple Trk receptors in a single rigorous study\",\n      \"pmids\": [\"9927421\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"NGF activates a protein kinase (120 and 104 kDa proteins) directly associated with p75(NGFR), co-immunoprecipitated from dorsal root ganglion and PC12 cells. TrkA activation was necessary to elicit p75(NGFR)-associated kinase activity. A 43 amino acid region in the cytoplasmic domain of p75(NGFR) was responsible for accelerating kinase activation at low NGF concentrations, even when NGF binding to p75(NGFR) was not required.\",\n      \"method\": \"Co-immunoprecipitation, kinase assay, deletion analysis\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP kinase assay with deletion analysis, single lab, two orthogonal methods\",\n      \"pmids\": [\"8698038\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"p75NTR overexpression in primary cortical neurons, PC12 cells, and glioma cells activates JNK, causes cytosolic cytochrome c accumulation, and activates caspases 9, 6, and 3. p75NTR-dependent JNK activation leads to phosphorylation and oligomerization of the BH3-domain-only family member Bad. Loss-of-function using Bad dominant negatives or RNA interference demonstrated a requirement for Bad in p75NTR-induced apoptosis.\",\n      \"method\": \"Overexpression, loss-of-function (dominant negative, RNAi), biochemical assays for JNK activation, cytochrome c release, caspase activity\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (overexpression + dominant negative + RNAi + biochemical pathway assays) in multiple cell types in one study\",\n      \"pmids\": [\"14673001\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Crystal structure of proNGF complexed with p75NTR resolved at 3.75 Å reveals a 2:2 symmetric binding mode, contrasting with the asymmetric structure of mature NGF bound to p75NTR. The pro regions of proNGF are mostly disordered and two hairpin loops (loop 2) at the top of the NGF dimer undergo conformational changes compared to mature neurotrophin structures. Surface plasmon resonance and cell-based assays showed calcium ions promote formation of a stable ternary complex of proNGF-sortilin-p75NTR.\",\n      \"method\": \"X-ray crystallography, surface plasmon resonance, cell-based binding assays\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure plus SPR binding assays plus cell-based assays in a single rigorous structural/biochemical study\",\n      \"pmids\": [\"20036257\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"In PC12 cells, NGF induces rapid alpha-secretase- and gamma-secretase-dependent cleavage of p75NTR, releasing the intracellular domain (ICD) into the cytosol. This cleavage is mediated by Trk-dependent activation of MEK-Erk signaling and induction of alpha-secretase activity, and is independent of ligand binding to p75NTR. Neurons and PC12 cells lacking p75NTR show defects in neurotrophin-dependent Akt activation that are rescued by full-length p75NTR or the p75 ICD but not cleavage-resistant p75NTR. NGF-dependent growth arrest of PC12 cells requires p75NTR cleavage and ICD generation.\",\n      \"method\": \"Pharmacological inhibition of secretases, MEK-Erk pathway inhibition, p75NTR knockout neurons, rescue with full-length vs cleavage-resistant constructs, Akt activation assays\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal approaches (pharmacological, genetic KO, domain rescue constructs, functional assays) in a single study\",\n      \"pmids\": [\"20530577\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"p75NTR predominantly assembles as a trimer (with monomers and trimers coexisting at the cell surface), as determined by biochemical techniques in vitro and in mouse brain tissue. Trimers are not required for ligand-independent or ligand-dependent p75NTR activation in a growth cone retraction functional assay; monomers are capable of inducing acute morphological effects in neurons.\",\n      \"method\": \"Biochemical oligomerization assays (in vitro and mouse brain tissue), functional growth cone retraction assay\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — biochemical and functional assays in a single study, single lab\",\n      \"pmids\": [\"26311773\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"NMR spectroscopy of p75NTR transmembrane and intracellular domains in lipid-protein nanodiscs revealed high flexibility and disorder in the juxtamembrane chopper domain, resulting in motions of the death domain being uncoupled from the transmembrane helix. Neither intracellular domain demonstrated propensity to interact with the membrane or to self-associate under these conditions.\",\n      \"method\": \"Solution NMR spectroscopy in lipid-protein nanodiscs\",\n      \"journal\": \"Biophysical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — NMR structural data in a defined reconstituted system, single lab, no functional mutagenesis validation\",\n      \"pmids\": [\"26287629\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"SC1 (Schwann cell factor 1), a p75NTR-interacting protein, acts as a transcriptional repressor requiring trichostatin A-sensitive HDAC activity (forming a complex with HDACs 1, 2, and 3). SC1 represses the cyclin E promoter, suggesting a mechanism for growth arrest. The zinc finger and PR domains are required for repressive activity, efficient block of BrdU incorporation, and nuclear localization.\",\n      \"method\": \"Gal4 tethering transcriptional assay, HDAC co-immunoprecipitation, promoter reporter assay, domain deletion analysis, BrdU incorporation\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with HDACs, functional reporter assays, domain mapping, single lab\",\n      \"pmids\": [\"15051733\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"IGF-1 receptor (IGF1-R) signaling, through IRS2, PIP3/Akt, and regulated by PTEN and p44 (short isoform of p53), controls the age-dependent switch from TrkA to p75NTR expression in human neuroblastoma lines and primary mouse neurons. This TrkA-to-p75NTR switch is accompanied by ceramide activation, BACE1 stabilization, and increased amyloid beta-peptide production.\",\n      \"method\": \"Signaling pathway manipulation (IGF1-R, PTEN, p44 transgenic mice), biochemical assays for ceramide, BACE1, and Abeta\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — transgenic animal model with multiple biochemical readouts, single lab\",\n      \"pmids\": [\"16619032\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"proBDNF activates p75NTR to suppress persistent firing and excitability of entorhinal cortex layer V pyramidal neurons via a Rac1-dependent and PIP2-dependent signaling cascade. proBDNF decreases cholinergic calcium responses in cortical neurons and affects carbachol-induced depletion of PIP2. Genetic deletion of p75NTR specifically in neurons or during adulthood enhances excitability and persistent firing.\",\n      \"method\": \"Electrophysiological recordings, p75NTR null mice, conditional/inducible p75NTR deletion, function-blocking antibodies, pharmacological probes\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (electrophysiology, genetic KO, antibody blockade, pharmacology) with consistent results across approaches\",\n      \"pmids\": [\"26134656\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Osmotic swelling-induced cell swelling activates transcription of the p75NTR gene via a pathway requiring phospholipase C, protein kinase C, and nitric-oxide synthase activity, independent of de novo protein synthesis.\",\n      \"method\": \"Reporter gene assay, pharmacological inhibition of PLC, PKC, NOS, tonicity manipulation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — pharmacological pathway dissection with reporter assay, single lab, multiple inhibitors tested\",\n      \"pmids\": [\"12821676\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"proNGF induces tau phosphorylation via p75NTR through the AKT/GSK3β pathway in vitro. Genetic reduction of p75NTR in P301L transgenic mice rescued memory deficits, alleviated tau hyperphosphorylation, and restored AKT/GSK3β pathway activity.\",\n      \"method\": \"In vitro proNGF treatment, p75NTR genetic reduction in transgenic mice, biochemical pathway analysis (AKT/GSK3β)\",\n      \"journal\": \"Molecular psychiatry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro mechanistic assay plus in vivo genetic model with pathway readout, single lab\",\n      \"pmids\": [\"29867188\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Two Nogo-66-derived peptides (Pep4 and NEP1-40) that modulate NgR-mediated neurite outgrowth inhibition also prevent NGF-stimulated p75NTR-dependent death of cultured embryonic motor neurons and protect spinal cord motor neurons after neonatal sciatic nerve axotomy, demonstrating that NgR antagonizes p75NTR-dependent motor neuron death.\",\n      \"method\": \"Cultured embryonic motor neuron survival assay, neonatal sciatic nerve axotomy in vivo\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro and in vivo convergent results, single lab, peptide-based functional inhibition\",\n      \"pmids\": [\"18182498\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Melanoma-derived small extracellular vesicles (sEVs) enriched in NGFR spread through the lymphatic system and are taken up by lymphatic endothelial cells, inducing ERK kinase and NF-κB activation and ICAM-1 expression to enhance lymphangiogenesis and tumor cell adhesion. Ablation or inhibition of NGFR in sEVs reversed the lymphangiogenic phenotype and decreased lymph node metastasis in pre-clinical models.\",\n      \"method\": \"sEV isolation and characterization, NGFR ablation/inhibition in sEVs, in vivo murine lymphangiogenesis/metastasis models, signaling pathway analysis (ERK, NF-κB, ICAM-1)\",\n      \"journal\": \"Nature cancer\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — mechanistic pathway elucidation with NGFR ablation/inhibition rescue experiments in both in vitro and in vivo models, multiple readouts\",\n      \"pmids\": [\"34957415\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"In melanoma, CD271 (NGFR) plays a dual role in phenotype switching: the cleaved intracellular domain controls proliferation, while interaction of CD271 with TrkA modulates cell adhesiveness through dynamic regulation of cholesterol synthesis genes.\",\n      \"method\": \"CD271 expression manipulation, analysis of intracellular domain cleavage products, TrkA interaction studies, gene expression profiling of cholesterol synthesis genes\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — functional domain analysis and interaction study, single lab, mechanistic follow-up but limited reconstitution data available from abstract\",\n      \"pmids\": [\"29215016\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"CD271 knockdown in hypopharyngeal cancer cells completely suppressed tumor-forming capability, induced cell-cycle arrest in G0, suppressed ERK phosphorylation, and strongly upregulated CDKN1C. Double knockdown of CD271 and CDKN1C partially rescued cells from G0 arrest. Inhibition of CD271-RhoA signaling by TAT-Pep5 diminished in vitro migration capability.\",\n      \"method\": \"siRNA knockdown, in vivo/in vitro tumor formation assays, ERK phosphorylation assay, double knockdown epistasis, RhoA pathway inhibition\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — epistasis (double knockdown rescue) plus pathway inhibition, single lab\",\n      \"pmids\": [\"27469492\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Induced expression of Ngfr in the hippocampus of APP/PS1dE9 mice suppressed reactive astrocyte marker Lipocalin-2 (Lcn2), which itself reduced neurogenesis in astroglia. Anti-neurogenic effects of Lcn2 were mediated by Slc22a17; blockage of Slc22a17 recapitulated the pro-neurogenic effect of Ngfr. Long-term Ngfr expression reduced amyloid plaques and tau phosphorylation.\",\n      \"method\": \"In vivo Ngfr overexpression, histological analysis, single-cell transcriptomics, spatial proteomics, functional knockdown of Lcn2 and Slc22a17\",\n      \"journal\": \"NPJ Regenerative medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo genetic manipulation with multiple orthogonal readouts (scRNA-seq, spatial proteomics, functional knockdown), single lab\",\n      \"pmids\": [\"37429840\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"SorCS3 co-localizes with and binds to p75NTR in GBM cells (confirmed by immunofluorescence and Co-IP), promoting endosomal trafficking of p75NTR to the lysosome for degradation, thereby reducing p75NTR protein levels and suppressing NGF/p75NTR-driven cell invasion and proliferation.\",\n      \"method\": \"Co-immunoprecipitation, immunofluorescence co-localization, endosomal trafficking assays, proliferation/invasion assays\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — Co-IP plus co-localization plus functional assays, single lab\",\n      \"pmids\": [\"35393432\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"p75NTR is expressed on plasmacytoid dendritic cells (pDCs) and its activation modulates immune function through TLR9 signaling, involving differential phosphorylation of interferon regulatory factor 3 and 7. p75NTR activation of pDCs influenced allergen-specific T cell proliferation and cytokine secretion in an NGF concentration-dependent manner.\",\n      \"method\": \"p75NTR expression characterization on pDCs, TLR9 activation assays, IRF3/7 phosphorylation, T cell proliferation co-culture assays, ovalbumin-induced asthma mouse model\",\n      \"journal\": \"Frontiers in immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mechanistic signaling assays combined with in vivo model, single lab\",\n      \"pmids\": [\"28861085\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"NGFR expression in melanoma drives resistance to T cell attack and BRAF+MEK inhibitors. NGFRhi cells induce the neurotrophic factor BDNF, which contributes to T cell resistance. Pharmacologic NGFR inhibition restores tumor sensitivity to T cell attack in vitro and in melanoma xenografts.\",\n      \"method\": \"Chronic T cell exposure selection, BRAF+MEK inhibitor treatment, BDNF functional assays, pharmacological NGFR inhibition, melanoma xenograft models\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional rescue by NGFR inhibition in vitro and in vivo, BDNF mechanism identified, single lab\",\n      \"pmids\": [\"32770055\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"p75NTR knockout mice exhibit reduced alveolar bone mass. p75NTR positively regulates osteogenic differentiation of ectomesenchymal stem cells (EMSCs) via the PI3K/Akt/β-catenin pathway. The promotive effect of p75NTR overexpression was attenuated by PI3K inhibitor LY294002, and the inhibitory effect of p75NTR knockdown on Runx2 and Col1 expression was reversed by PI3K agonist 740Y-P.\",\n      \"method\": \"p75NTR knockout mice, micro-CT, RNA-sequencing, lentiviral p75NTR overexpression/knockdown, PI3K pathway pharmacological manipulation\",\n      \"journal\": \"Cell proliferation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO plus pharmacological epistasis with pathway agonist/antagonist, single lab\",\n      \"pmids\": [\"32215984\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"In denervated skeletal muscle, pro-BDNF and p75NTR are significantly upregulated, and JNK and NF-κB downstream pathways are activated along with muscle atrophy and inflammation. p75NTR inhibition using LM11A-31 significantly reduced JNK activation and inflammatory cytokines in denervated muscle. Skeletal muscle-specific BDNF knockout reduced pro-BDNF levels, JNK activation, and inflammation.\",\n      \"method\": \"Sciatic nerve denervation mouse model, p75NTR inhibitor (LM11A-31), skeletal muscle-specific BDNF KO, Western blot, tissue staining\",\n      \"journal\": \"Life sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological inhibition and genetic KO with consistent results, single lab\",\n      \"pmids\": [\"34678261\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"In denervated skeletal muscle, glial cells express Ngfr and are located near neuromuscular junctions close to Thy1/CD90-expressing cells, which provide the main cellular source of NGF post-denervation. Functional communication between these cells is mediated by NGF/NGFR, as recombinant NGF or co-culture with Thy1/CD90-expressing cells increased glial cell number ex vivo.\",\n      \"method\": \"scRNA-seq/snATAC-seq, sciatic nerve transection model, ex vivo co-culture, recombinant NGF treatment\",\n      \"journal\": \"iScience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — single-cell genomics plus functional ex vivo co-culture assay, single lab\",\n      \"pmids\": [\"37416457\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"NGFR expression in melanoma cells leads to down-regulation of NK cell activating ligands and up-regulation of stearoyl-coenzyme A desaturase (SCD), protecting melanoma cells from NK cell-mediated killing. Pharmacological and siRNA-mediated inhibition of SCD reversed NGFR-induced NK cell evasion in vitro and in vivo.\",\n      \"method\": \"In vitro and in vivo NK cell cytotoxic assays, NGFR overexpression, SCD pharmacological inhibition, SCD siRNA knockdown, mouse metastasis model with adoptively transferred human NK cells\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — mechanistic pathway (NGFR→SCD→NK evasion) validated by both pharmacological and genetic (siRNA) inhibition in vitro and in vivo, convergent results\",\n      \"pmids\": [\"36638181\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"p75NTR in retinal glia and pericytes mediates ligand-dependent (proNGF) induction of inflammatory cytokines, disruption of the neuro-glia-vascular unit, promotion of blood-retina barrier breakdown, edema, and neuronal death in a streptozotocin mouse model of diabetic retinopathy. p75NTR-dependent inflammation leads to ischemia and pathological angiogenesis through Semaphorin 3A. Antagonists of p75NTR or proNGF suppressed each phase of pathology.\",\n      \"method\": \"Streptozotocin diabetic retinopathy mouse model, oxygen-induced retinopathy model, p75NTR and proNGF antagonists\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological antagonism in two in vivo disease models with multiple pathway readouts, single lab\",\n      \"pmids\": [\"27559166\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"CD271/p75NTR inhibits the differentiation of mesenchymal stem cells into osteogenic, adipogenic, chondrogenic, and myogenic lineages. CD271+ DDPSCs showed inhibited differentiation into osteoblasts and adipocytes compared to CD271- cells. Forced expression of CD271 in C3H10T1/2 cells (10T271) inhibited differentiation into all four lineages.\",\n      \"method\": \"FACS sorting of CD271+ subpopulations, forced CD271 overexpression in C3H10T1/2 cells, in vitro multilineage differentiation assays\",\n      \"journal\": \"Stem cells and development\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — gain-of-function overexpression plus sorted subpopulation comparison across multiple lineages, single lab\",\n      \"pmids\": [\"21142793\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"In valproic acid (VPA)-treated neuroblastoma cells, p75NTR and sortilin are upregulated via HDAC inhibition leading to decreased EZH2 and upregulation of transcription factor CASZ1, a positive regulator of p75NTR. VPA favored proNGF-induced p75NTR/sortilin interaction and enhanced JNK activation and apoptosis. Depletion of p75NTR or blocking proNGF/sortilin interaction (neurotensin) reduced apoptotic response.\",\n      \"method\": \"HDAC inhibitor treatment, EZH2/CASZ1 knockdown, p75NTR and sortilin knockdown, proNGF treatment, JNK activation assay, apoptosis assays\",\n      \"journal\": \"Apoptosis\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — multiple knockdown approaches with consistent apoptosis readout, single lab\",\n      \"pmids\": [\"32712736\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"NGFR knockdown in murine OSCC cells suppressed tumor invasion and metastasis. NGF treatment of NGFR+ OSCC cells increased ESM1 (endocan) expression. ESM1 overexpression conferred an enhanced migratory, invasive, and metastatic phenotype. ESM1 shRNA knockdown in NGFR-overexpressing OSCC cells abrogated tumor growth kinetics and invasive/metastatic properties, placing ESM1 downstream of NGFR in regulating OSCC invasion.\",\n      \"method\": \"NGFR overexpression/knockdown, NGF stimulation, gene expression array, ESM1 overexpression, ESM1 shRNA knockdown, in vitro migration/invasion assays, in vivo metastasis model\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — epistasis (NGFR→ESM1 pathway) established by rescue/knockdown experiments in vitro and in vivo, single lab\",\n      \"pmids\": [\"27683113\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Stable shRNA-mediated knockdown of CD271 in patient-derived melanoma cells abrogated tumor-initiating and colony-forming capacity. Genome-wide expression profiling linked CD271 to SOX10 and a neural crest stem cell (NCSC) signature, and connected CD271 expression to CD133.\",\n      \"method\": \"shRNA knockdown, in vivo tumor-initiating assay, genome-wide expression profiling, gene-set enrichment analysis\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — stable loss-of-function with defined functional phenotype plus transcriptomic pathway analysis, single lab\",\n      \"pmids\": [\"24799129\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"In human epidermis, CD271 overexpression provokes the switch of keratinocyte stem cells (KSCs) to transit-amplifying (TA) cells, while silencing CD271 induced TA cells to revert to a KSC phenotype (assessed by β1-integrin expression and increased clonogenic ability). CD271(+) TA cells expressed more survivin and keratin 15 and displayed higher proliferative capacity.\",\n      \"method\": \"CD271 overexpression, siRNA silencing, FACS sorting, clonogenic assay, skin equivalent models\",\n      \"journal\": \"The Journal of investigative dermatology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — gain- and loss-of-function with multiple functional readouts, single lab\",\n      \"pmids\": [\"25330297\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"NGFR/p75NTR is a multifunctional TNFR superfamily member that physically interacts with Trk receptor tyrosine kinases (TrkA/B/C) through both extracellular and intracellular domains to modulate neurotrophin signaling specificity; undergoes Trk-induced alpha/gamma-secretase-dependent cleavage to release an intracellular domain that potentiates Akt signaling and growth arrest; signals apoptosis through JNK-mediated Bad phosphorylation and cytochrome c/caspase cascade activation; predominantly assembles as a trimer at the cell surface with monomers capable of acute morphological signaling; binds proNGF in a 2:2 symmetric complex (structurally distinct from mature NGF binding) and promotes pro-apoptotic signaling through sortilin co-receptor; activates p75NTR-Rac1-PI4K/PIP2 pathway to suppress cortical pyramidal neuron excitability; mediates osteogenic differentiation via PI3K/Akt/β-catenin signaling; in melanoma, drives immune evasion by upregulating stearoyl-CoA desaturase (SCD) to escape NK cell killing and promotes metastasis via sEV-mediated ERK/NF-κB/ICAM-1 activation in lymphatic endothelial cells; and in cancer contexts acts downstream of NGFR through ESM1 to drive invasion and metastasis.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"NGFR (p75NTR), a TNF-receptor superfamily neurotrophin receptor, integrates neurotrophin signaling by physically partnering with the Trk receptor tyrosine kinases TrkA, TrkB, and TrkC through both its extracellular and intracellular domains, an interaction dependent on Trk autophosphorylation that sharpens ligand specificity of Trk activation [#0]. The receptor binds the unprocessed precursor proNGF in a 2:2 symmetric mode distinct from mature NGF, and calcium promotes assembly of a stable proNGF–sortilin–p75NTR ternary complex that drives pro-apoptotic signaling [#3]. p75NTR couples to opposing fates depending on context: it triggers apoptosis via JNK-dependent phosphorylation and oligomerization of Bad, cytochrome c release, and caspase-9/6/3 activation [#2], yet upon NGF stimulation it also undergoes Trk/MEK-Erk-driven alpha- and gamma-secretase cleavage that releases an intracellular domain required for neurotrophin-dependent Akt activation and growth arrest [#4]. In the nervous system the receptor controls neuronal excitability through a proBDNF-activated Rac1/PIP2 cascade [#9] and contributes to pathological tau phosphorylation via AKT/GSK3β [#11]. Beyond neurons, NGFR is a major driver in melanoma and other cancers, where it promotes immune evasion by upregulating stearoyl-CoA desaturase to escape NK-cell killing [#23], enhances T-cell and BRAF/MEK-inhibitor resistance through BDNF induction [#19], and spreads via NGFR-enriched extracellular vesicles that activate ERK/NF-κB/ICAM-1 in lymphatic endothelium to promote metastasis [#13]. It also regulates stem-cell differentiation, both inhibiting multilineage mesenchymal differentiation [#25] and positively driving osteogenic differentiation through PI3K/Akt/β-catenin [#20].\",\n  \"teleology\": [\n    {\n      \"year\": 1996,\n      \"claim\": \"Established that NGF signaling engages an enzymatic activity physically associated with p75NTR, indicating the receptor is not merely a passive binding protein but a signaling platform.\",\n      \"evidence\": \"Co-IP kinase assay and cytoplasmic-domain deletion analysis in dorsal root ganglion and PC12 cells\",\n      \"pmids\": [\"8698038\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"The identity of the associated 120/104 kDa kinase was not established\", \"Whether the kinase association is direct or bridged by another protein is unresolved\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Defined the physical basis for crosstalk between p75NTR and the Trk family, showing p75NTR directly modulates Trk ligand selectivity.\",\n      \"evidence\": \"Reciprocal Co-IP with deletion constructs and kinase inhibition across TrkA/B/C in transfected cells\",\n      \"pmids\": [\"9927421\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry and structural interface of the Trk–p75NTR complex not defined\", \"Whether the interaction is constitutive or ligand-induced in vivo unclear\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Elucidated the apoptotic effector arm of p75NTR, linking it through JNK to the intrinsic mitochondrial cell-death machinery.\",\n      \"evidence\": \"Overexpression plus dominant-negative and RNAi loss-of-function with biochemical JNK/cytochrome c/caspase readouts in multiple cell types\",\n      \"pmids\": [\"14673001\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How ligand engagement activates JNK upstream of Bad is not defined\", \"Does not address how the apoptotic versus survival decision is selected\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Resolved the structural distinction between proNGF and mature NGF recognition, explaining how the precursor selectively drives the pro-apoptotic co-receptor complex.\",\n      \"evidence\": \"X-ray crystallography of proNGF–p75NTR, SPR, and cell-based ternary complex assays\",\n      \"pmids\": [\"20036257\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structure of the full proNGF–sortilin–p75NTR ternary assembly not solved\", \"Role of the disordered pro region in signaling not defined\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Identified regulated intramembrane proteolysis as the mechanism converting p75NTR into a soluble intracellular signaling effector that potentiates Akt and growth arrest.\",\n      \"evidence\": \"Secretase and MEK-Erk inhibition, p75NTR-knockout neurons, and rescue with cleavage-resistant vs intact constructs in PC12 cells\",\n      \"pmids\": [\"20530577\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct molecular targets of the released ICD not identified\", \"How the ICD potentiates Akt mechanistically unresolved\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Clarified the oligomeric state of the receptor, showing trimers predominate but are dispensable for acute morphological signaling carried by monomers.\",\n      \"evidence\": \"Biochemical oligomerization assays in vitro and in mouse brain plus growth cone retraction functional assay\",\n      \"pmids\": [\"26311773\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Which signaling outputs require trimers versus monomers is not fully mapped\", \"Single lab, no orthogonal structural validation\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Connected p75NTR to control of cortical neuron excitability through a defined Rac1/PIP2 signaling cascade activated by proBDNF.\",\n      \"evidence\": \"Electrophysiology with constitutive, conditional, and inducible p75NTR deletion plus antibody blockade and pharmacology\",\n      \"pmids\": [\"26134656\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct molecular link from p75NTR to Rac1 not defined\", \"Whether sortilin participates in this pathway not tested\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Defined opposing roles of p75NTR in stem-cell fate, demonstrating it drives osteogenic differentiation via PI3K/Akt/β-catenin in vivo.\",\n      \"evidence\": \"p75NTR-knockout mice, micro-CT, and PI3K agonist/antagonist epistasis in ectomesenchymal stem cells\",\n      \"pmids\": [\"32215984\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Reconciliation with reports of p75NTR inhibiting multilineage differentiation not addressed\", \"How p75NTR activates PI3K upstream is unclear\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Revealed a non-cell-autonomous metastatic mechanism in which NGFR cargo in extracellular vesicles reprograms lymphatic endothelium.\",\n      \"evidence\": \"sEV isolation with NGFR ablation/inhibition and in vivo lymphangiogenesis/metastasis models with ERK/NF-κB/ICAM-1 readouts\",\n      \"pmids\": [\"34957415\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How NGFR in sEVs activates recipient-cell ERK/NF-κB mechanistically not defined\", \"Receptor for NGFR-bearing sEVs on endothelial cells not identified\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Established NGFR as a driver of NK-cell immune evasion in melanoma through metabolic rewiring via stearoyl-CoA desaturase.\",\n      \"evidence\": \"NK cytotoxicity assays with NGFR overexpression and SCD pharmacological/siRNA inhibition in vitro and in metastasis models\",\n      \"pmids\": [\"36638181\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How NGFR transcriptionally controls SCD and NK ligands is not defined\", \"Whether SCD-driven lipid changes act on NK ligands or membrane properties unresolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How a single receptor selects between pro-apoptotic, pro-survival, differentiation, and oncogenic immune-evasion outputs across cell types remains the central unresolved question.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model of how co-receptor (sortilin, Trk), oligomeric state, and proteolysis jointly determine output\", \"Direct intracellular effectors of the cleaved ICD remain unidentified\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 3, 9]},\n      {\"term_id\": \"GO:0048018\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [5]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [4]},\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [17]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 4, 9]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [23, 19]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [13, 23]}\n    ],\n    \"complexes\": [\n      \"proNGF–sortilin–p75NTR ternary complex\"\n    ],\n    \"partners\": [\n      \"TrkA\",\n      \"TrkB\",\n      \"TrkC\",\n      \"sortilin\",\n      \"SorCS3\",\n      \"SC1\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}